This invention pertains to a mobile grading machine and more particularly to one in which separate means can be readily operated either selectively or automatically in order to properly position the grading blade as well as to lift the entire grading assembly from the ground in order to permit relatively simple maneuvering of the grading machine.
Heretofore, land leveling machines and equipment have typically been characterized by an elongate frame structure pivotally mounted to a tongue to be drawn by a tractor or other hauling vehicle. Grading machines of the foregoing type have a number of disadvantages when it is desired to precisely grade a plot of ground. Where the plot of ground is relatively small a significant portion of the plot will be difficult, if not impossible, to reach using a conventional grading machine of the kind described and as referred to in FIG. 2.
Accordingly, the corners of such a plot will typically remain ungraded due to the inability of the apparatus to readily obtain access fully into such corners.
As will be readily evident from the description which follows according to the method of the invention a grading machine 20 as disclosed herein is capable of being backed up very closely to the side of a plot of ground so as to grade substantially all of the ground within the given plot.
Further, as well be disclosed further below the method presented in FIG. 3 further includes the step of lifting the blade clear of the ground by lifting the grading machine entirely off of the ground while backing grading machine 20 into the corner.
Thus, as shown in FIG. 2, as known in the prior art, a tractor 10 or other towing means is coupled to a grading machine 11 by means of a tongue 12. Machine 11 includes an elongate rigid frame 15, a fixed axle 13 at the trailing end thereof which carries a pair of wheels 14 on its ends, and a steering axle 16 which supports the leading end of frame 15 to guide grading machine 11 under control of the direction of tongue 12. Thus axle 16 pivots about an axis normal to the supporting surface thereunder. Frame 15 carries a grading blade 19 substantially midway between the ends thereof.
Typically grading machines of the type shown in FIG. 2 have a substantial length whereby it will be readily evident that the ungraded portion 17 remaining within a corner angle 18 will be substantial.
According to Applicant's invention a mobile grading machine 20 of a type adapted to be drawn by a tractor 21 or other towing means is arranged to carry out the method of grading an angular corner of a plot of ground using the method described below after first grading as much of the corner as can be graded, such as along the path shown by arrow 24. From inspection and from the explanation further below it is readily evident that a smaller corner plot 26 remains to be graded after making the corner turn 24 using Applicant's construction than the corner plot 17 using that of the prior art. However, Applicant is further able to grade substantially all of the corner plot 26 by means of the method of backing the grading machine 20 in the direction of one of the arrowheads 22, 23 so as to back the grading machine into the corner alongside a first side 27, 29 of the corner angle with the grading blade of the grading machine raised to a position clear of the ground. Next the grading blade is lowered followed by moving grading machine 20 forwardly out of the corner in the direction of arrowhead 28, 31 so as to grade a first portion of the corner. The next step is to back the grading machine 20 into the corner alongside a second side 27, 29 of the corner angle with the grading blade raised clear of the ground followed by lowering the blade into grading relation with the ground. Then machine 20 is moved forwardly in the direction of arrowhead 31,28 out of the corner so as to grade a second portion of the corner plot partially overlapping the first portion thereby grading the ground within the corner.
As is known, lasers have been employed heretofore in conjunction with grading machines for controlling the position of the grading blade so as to achieve a predetermined grading angle. Typically, a laser generator serves to rotate and project a laser beam in a manner defining a plane of energy adapted to be received by a sensor carried by the grading machine. In response to determining that the sensor has dropped below the "plane" of energy, means are activated for lifting the blade so as not to remove any more material at that "low" point. Similarly, if the sensor detects that it has moved above the plane of energy, means are activated for moving the blade downwardly in order to remove the "high" surface irregularity which has caused the sensor to be moved above the plane of energy. In using apparatus of the kind shown in FIG. 2, if the laser sensor is mounted immediately above the blade it is readily evident that the blade will be activated prematurely in response to the fact that the wheels carried on axle 16 will move up and down in terrain following movement well before blade 19 is adjacent the low or high surface. This movement of axle 16 clearly causes the sensor to move up and down in terrain following movement prematurely. When the sensor is lifted upwardly in terrain following movement it will cause the blade 19 to move downwardly to remove the raised ground surface detected by the front wheels rather than by means disposed proximate blade 19. Accordingly, a gouge will be cut prematurely in advance of the "high" surface (which earlier caused the sensor to indicate that there was a raised surface beneath blade 19) when there was none.